package yukicoder111; import java.util.Scanner; public class Main { public static void main(String[] args){ Scanner sc=new Scanner(System.in); int len=sc.nextInt(); int[] dp=new int[len+1]; long ans=0; int nlen=len; while(nlen>=3){ ans+=len-nlen+1; nlen-=2; //abababababababa 15 //ababababababa //babababababab //abababababa //bababababab //ababababa //babababab //abababa //bababab //ababa //babab //aba //bab } System.out.println(ans); } }